With every new Mac and every new Mac OS X version, the Migration Assistant …

I got my first Mac, an iBook, in 2002. It ran Mac OS 10.2 Jaguar. Since then, I've migrated my electronic life to new hardware three times and to a new OS version four times. I'm sure the Migration Assistant can assist me in moving from my MacBook running 10.6 to a new MacBook Air running 10.7 without trouble. But after almost a decade, I'm ready to make a clean break and start from scratch, only migrating my data—no applications, libraries, or the cruft that has built up in nooks and crannies of the system.

Although all of this is inspired by the imminent arrival of Mac OS 10.7 Lion, the information here is not Lion-specific; I have tested the various migration tactics on Snow Leopard. However, most of them are more application- than OS-specific.

Why bother?

Migrating by hand is a lot of work and carries the risk of even more work down the road if something isn't migrated properly and has to be restored from backups.

Some Ars staffers (who shall remain nameless) suggested that I should just clone my old drive to the new one and then run the Lion upgrade process. Disk cloning is a good way to get up and running again after replacing a hard drive, but it's not a good idea if the new machine is released with a newer version of the OS. The new hardware might require drivers that the OS on the old system doesn't have yet. If you want the least amount of trouble, the best migration strategy is to let the Mac OS installer or the Migration Assistant do their thing. This has worked extremely well for me for the past nine years.

So why attempt a manual migration at this point? Four reasons: applications, settings, bloated iLife libraries, and cruft left behind in the Library folder.

When I ran the System Profiler and looked at System/Applications to see the list of applications installed on my system, I was surprised at how many applications and tools had managed to snag a spot on my hard drive over the years. My system seems to be a Roach Motel for applications.

The applications in the list range from multiple copies of my scanner software to Yahoo Sync to various ancient Adobe tools to links to Windows applications on a non-existent Boot Camp partition installed by Parallels Desktop.

Some judicious uninstalling would help, or I could tell the Migration Assistant not to bring over applications. But that would still leave all kinds of settings and other application data hanging around in my Library folder.

Another reason to start from scratch is so all my settings are reset to the system defaults. For instance, when I wrote the iWork'09 review, I noticed that the applications had gained new icons in the toolbar. But because I had already customized the toolbar with an earlier version of each application, I never saw the new icons. I'm sure there are lots of examples of new or improved options in Mac OS that I've never noticed because the settings I've been using for years make them invisible. By not bringing over any of my existing settings, I get to experience the Mac the Way Steve Jobs Intended. (For a while, at least, until I turn off everything I find annoying.)

Then there are the iLife libraries. My iTunes and iPhoto libraries add up to 100GB of disk space, and especially in the case of iPhoto, I suspect that there's a good amount of waste. iPhoto reports 44.4GB worth of photos, but the disk space taken up by the iPhoto library is 64.4GB. I really want to find out if the extra 20GB is legitimate overhead—iPhoto needs to store thumbnails and such—or cruft that has built up in nooks and crannies of my iPhoto library.

There's also that other library: the Library folder in my home folder. It holds 11.8GB worth of data, including 6.8GB of mail. I'm sure some of that other 5GB has a legitimate purpose, but there's also lots of settings and support data for defunct applications hanging around in there. Manually going over the 300,000 or so files doesn't appeal to me; neither does leaving all these old settings intact. If I ever reinstall one of those applications, I want them to have that fresh app smell, not be hampered by settings left over from an older version.

So although there is no absolute need to start clean and bring over everything that needs to be brought over by hand, the reasons above are compelling to me at this point in time. A big reason for that is the fact that I've migrated my system at least seven times in nine years, and the confluence of a new Mac OS version and a new computer makes for the perfect opportunity to attempt such an undertaking. But I'm the first to agree that this is not for everyone.

The network

I don't recommend doing a manual migration with the same machine as the source and the destination, because then you can't have the old and the new system side by side. Everything will be harder to do (and riskier). Therefore, I'm assuming you have a new machine straight out of the box sitting next to an older one that has all your data and settings on it.

The first order of business is setting up some networking. The ideal situation is one where both machines are hooked up to your home network (and, through this, the Internet) using Ethernet. If your computers both have Ethernet ports, but you can't connect them to your home network that way; you may want to turn off WiFi and connect the two computers using a direct cable when the time comes to copy over large amounts of data. Having both the direct cable and WiFi connected usually doesn't work well because the data often still goes over the slower WiFi link. You only have to turn off WiFi on one of the computers to force transfers through the cable.

Gigabit Ethernet is fast!

You may also want to use a direct Ethernet cable if both machines have Gigabit Ethernet but your home network is limited to 100Mbps Ethernet. Direct connections require no setup; just plug in the cable and the machines should automatically "see" the services the other one is advertising. You should be able to turn the WiFi back on once the transfer is going without trouble.

If only one system has Ethernet, your fastest option is to connect that computer to a LAN port on your WiFi base station and use WiFi on the computer that doesn't have Ethernet. That way, the WiFi base station can dedicate the full WiFi bandwidth towards the Ethernet-less computer rather than first receiving packets from one computer wirelessly and then sending them out to the other wirelessly, which effectively cuts the WiFi bandwidth in half.

In order to transfer data, you need to set up one computer for File Sharing in the Sharing section of the System Preferences. I prefer to let my secondary system do all the sharing, so if the unthinkable happens and someone gains access to the machine over the network, at least it's not my main computer, where I do my online banking and so on, that's compromised.

You can connect to the sharing computer's drives from the other computer by simply clicking on its name in the sidebar of a Finder window and then clicking on "Connect As" to log in.

A new password

As long as we're being paranoid, you may also want to pick a new password for your new account on your new computer at this time. Remember that advice on strong passwords typically applies to situations where offline password guessing is an issue. This is not the case for your account password as long as the guesser doesn't have your Mac—or your backups!—in their possession, so you don't necessarily need a password consisting of 14 or more completely random characters. That never hurts, though.

I personally use a password that has eight pretty random characters. As I have to type it several times a day, forgetting the password is not a (big) issue, but excessive length would be. I also wrote it down on something in a very safe place and don't use it for anything other than my account on my Mac.

1. Carbon Copy Cloner to my HDD, making a 1:1 image of my disk onto an external drive2. Boot into the Mac install with the disk and format my HDD3. Install OS fresh4. Run updates5. Copy over personal files like images, videos, documents, downloads6. Look at list of apps in my Application folder, and re-download+install what I need then and there7. Install the rest when needed

No need for the massive article.

Call me crazy but I've never used the migration assistant. I've gone from Tiger to Leopard to Snow Leopard and soon Lion, and I always do a fresh install. Maybe it's a habit from my Windows days, but the feel of a fresh OS install is soothing for the soul.

I used to do clean installs of Mac OS, dating back to the Classic days. 2 things have happened since then:

1) I now have other things to do with my time than spend it on system maintenance. It's one of the reasons I use a Mac after all.

2) Apple has steadily improved the tech behind migrating data, apps & settings during OS upgrades. I wouldn't do a clean OS install on my iPhone, for example. Why should I do it with OS X?

I believe Snow Leopard was the first time I didn't bother doing a clean install, and I thought I was a holdout from a bygone era. I will be happily installing Lion over 10.6 without the huge effort and time of a clean install.

I say this not to diss the author/article, but rather because I think it's worthwhile to periodically reconsider whether old habits still serve a useful purpose.

You can migrate with your time machine backup. OSX installer automatically detects time machine backups and asks you if you want to restore from it. The 'clean install' is really just an easy method of cleanup for those who have too many rouge files and extensions and such and don't want to make the effort to clean them up.

One of the biggest reasons I use a Mac is because the system is designed to be easy to maintain. It even detects and automatically disables incompatible kexts for you. How much easier can they make it?

I just looked at the number of application listed in the System profiler on my system. 719. That's counting all the Windows links from Parallels and the 6 copies of Starcraft II (I guess it keeps every old version?) and all the additional inflation. I have 719 apps. That seems like an awfully large number.

My first Mac came with Tiger installed. Since then, each time Apple's released a new version of OS X, I've done a clean install.

Ten years ago, migrating from an old machine to a new machine or moving data around before formatting a hard drive was tedious and slow. As time's gone on, I find that this process has grown progressively easier.

External hard drives are invaluable for this. Since Apple introduced Time Machine, I've got one connected to my primary Mac at all times. I don't have much piecemeal data on my machines anymore that isn't already attached to an email in my Gmail account or in my Dropbox folder. One big thing that won't fit in either is my iTunes data. That's where the external hard drive comes in. Apple has an excellent article that describes the process of moving your iTunes folder from one machine to another. (It even works moving from Windows to Mac or vice versa.) The article walks you through using an iPod as a hard drive, but any external drive will do. http://support.apple.com/kb/HT1329?viewlocale=en_US

An external drive holds my iTunes and photos. (I don't use iPhoto.) Dropbox and Gmail get everything else. When I run the Mac OS X install DVD, I wipe out the existing data on the drive. Why? The same reasons mentioned in the article -- eliminating cruft, saving storage space, and getting that "just out of the box" feel of the operating system. I feel the same way about applications -- I like running software that hasn't been upgraded from older versions.

I maintain a list of must-have software and browser extensions, but waiting to install software until you need it make sense -- you might end up never installing software you don't need anymore. Google Chrome even syncs extensions.

I don't back up the Keychain at all. Instead, I use 1Password. It makes my life easier, and my passwords are more secure.

My backup procedure takes a few hours, unlike the procedure in the article, which the author claims takes a week. I usually back up and move everything, then sleep on it before doing the clean install.

With just a few hours of prep time, I get a like-new computer every time a new OS is released, or more often than that.

normally I'd agree but I've been running consecutive builds of 10.7 and now the GM without issue for a while now. As the saying goes, if it ain't broke, don't waste way too much time migrating your apps over.

I say this not to diss the author/article, but rather because I think it's worthwhile to periodically reconsider whether old habits still serve a useful purpose.

I think you have this wrong. That's EXACTLY what the author is doing. His old habit is to just migrate/upgrade, rather than a clean install. This time, he's clean installing.

There are a lot of useless files that get stored in Library. Both ~/Library and /Library, actually. One thing that shouldn't be overlooked is programs that require activation. Don't erase your OS until you deactivate them, or it will be incredibly frustrating to reinstall them. I'm looking at you, Adobe.

No offense, but this sounds like the most painful, drawn-out install process ever. I've used all three "big" OS's(win, nix, mac), and I've never spent more than 2-3 hours on a full install. It takes almost as much time to do a "migrate" as a clean install, so I've never done anything but that on most systems(well, except Ubuntu, I do theirs every two updates, once a year).

The only thing that takes longer than that is the mass data transfer(photos,music,etc), but I just start that before bed and let it work while I sleep. So, 2-3 hours of installation, sleep, and have a fresh new system in the morning.

I guess I'm just put off by the fact that I'm used to seeing a more common-sense, techie-oriented article on Ars, and this one reads like it was written by someone with relatively little tech experience.

When I installed Lion, I made sure my Time Machine backup had completed sometime today, and then pressed the 'Install' button, and walked away. It was literally one button press, plus my administrator password.

An hour later, I came back, and I have a Lion install with no issues.

The "must clean install" may have been good advice in the past, but that doesn't mean it is good advice today. Resetting PRAM used to fix everything too...

1. Carbon Copy Cloner to my HDD, making a 1:1 image of my disk onto an external drive2. Boot into the Mac install with the disk and format my HDD3. Install OS fresh4. Run updates5. Copy over personal files like images, videos, documents, downloads6. Look at list of apps in my Application folder, and re-download+install what I need then and there7. Install the rest when needed

No need for the massive article.

Call me crazy but I've never used the migration assistant. I've gone from Tiger to Leopard to Snow Leopard and soon Lion, and I always do a fresh install. Maybe it's a habit from my Windows days, but the feel of a fresh OS install is soothing for the soul.

This is what I do. However, I still get flack for doing this. "Why not just do an upgrade. Lion can upgrade from the drive, why install it from a disc/flash drive", and I don't get it.

This article is great just in case I ever do take that extra leap, because I do the same thing as you. Even though I have a clone that I can use the MA with, I just manually drag and drop all of my important bits back. The thing is, I do it about once a year to keep my OS clean, so while I can manage doing this, I couldn't perform the steps in the article every time.

The Flash installer asks for your password because it installs to the system Library (/Library/Internet Plug-Ins). It could not ask for your password (and install at ~/Library/Interet Plug-Ins), but then each individual user of Flash would have to install and maintain a copy of Flash. That sounds really bad for what is still an important plug-in.

Flash isn't an app, it's a system plug-in. It needs admin rights to install for all users.

Say you just did an upgrade, as is intended with this OS. Say you even had a backup and could use the Migration Assistant, what would the equivalent be for Windows?

How does Windows transfer over applications when a new OS comes out?

Did you originally have the 32-bit OS or the 64-bit installation? Which version do you have to get? Was it Home? Home Premium? Professional? Business? Enterprise? Ultimate? What's the proper upgrade path? Will all of my files transfer over? Is there a "special" USB transfer cable you have to get?

Oh yes. Base the entirety of Apple's OS upgrade strategy based on one fringe case. It's not like Windows users have any tough decisions to make when performing a standard upgrade or anything...

I install fresh too, have since 10.3, but not nearly in as convoluted of a way. I keep as many apps in ~/Applications as I can, and just rsync my home dir to my fileserver, then reinstall fresh and then rsync ~/Applications ~/Music and some choice pref files from ~/Library.

This article makes it sound like brain surgery, its not that big of a deal. While the files are copying I just quick setup the minimally few things I actually change, aka: dock on left and autohide, oh and install vmware again.

Then its back into emacs/chrome/terminal and back to work while large crap copies. You can also just copy the entire home dir straight up too if you wanted. Its about the same. I just use the new os as an excuse to get some prefpanes and other nonsense out of my home dir.

Its $HOME cleaning time basically, and since most everything sits in $HOME on my install, the upgrade parts don't buy me much. Also means the files get thrown down more sequentially again.

My sympathies for your pain. It's sad that Apple users are in just about the same unwieldy boat when it comes to a: figuring out what is important for an application (and whether it's user-specific data, temporary files, useful but easily re-created files)b: migrating an application between installs, either fresh or with user-specific data, without a lot of nonsense work

I've got saved games in my user folder, in my documents folder, in my program data, in my app data. I've got to rescue email from a folder in app data, easily automated once I found it, but aren't those really more part of my documents than app data? And I too save old install programs, but they were scattered over multiple DVDs and backup drives; many programs I once used, I've forgotten the locations and even the names. Maybe I've found something better since, or maybe I've made do with cobbled together alternatives. I'm not the sort to do clean reinstalls, but I've bought a lot of new computers and started fresh that way.

It seems like a modern OS should do a better job of keeping track of what programs install and access what files, and when, along with the ability to bundle up all those files a program touches that aren't a fundamental part of another program. Then you wouldn't have to fiddle with manually saving your user settings, and user data, and latest patches to program A. You'd just backup your apps the same way you backup your pictures or music (though your examples show those aren't straightforward either).

Say you just did an upgrade, as is intended with this OS. Say you even had a backup and could use the Migration Assistant, what would the equivalent be for Windows?

How does Windows transfer over applications when a new OS comes out?

Windows Easy Transfer (Part of Win7) is surprisingly good, actually. It'll bring over your data on a USB stick or external hard drive without much fuss. It won't copy over your apps, but that is a limitation of Windows, where apps have to be installed and can't be simply copied.

I recently used it to migrate my kids from XP to Win7 Home Premium, and it was relatively painless.

It seems like a modern OS should do a better job of keeping track of what programs install and access what files, and when, along with the ability to bundle up all those files a program touches that aren't a fundamental part of another program. Then you wouldn't have to fiddle with manually saving your user settings, and user data, and latest patches to program A. You'd just backup your apps the same way you backup your pictures or music (though your examples show those aren't straightforward either).

A modern OS should do this, and such modern OSes do exist. The problem is that you'll find them on your phone, but not on your PC.

I don't remember the last time I did a clean install and I don't plan on doing it for Lion. Just the occasional run through Onyx and Hazel takes care of removing support files for apps I delete. Hazel also takes care of archiving downloads and desktop items which I clean out when they grow too large.

Clean out when I have to little at a time. Drawing a line and doing everything at once just causes more work.

Don't forget that if you authorized an older machine to access certain iTunes/Audible content, you'll want to de-authorize it if you intend to get rid of that machine at some point.

Regarding fast file transfer, I hook the old machine up via Firewire and drag the entire home directory into a temporary sorting folder on the new one and pick through the files as needed Once everything important is in place on the new machine I delete the leftovers.

I try to do the same (keeping the /Applications folder clean except for Apple's own apps, bundled and purchased later), but there are some third-party apps that refuse to run anywhere other than at the root folder. I have no idea why they have a restriction on where they reside.

A few things I notice... You can use a firewire cable to create a network between two macs (if they both have ports) which is quite fast.

Also, there is a script that will embed downloaded artwork into your music files within iTunes so that if you just select all the tracks you want and then embed the artwork. You don't need to go through the manual process of copy/pasting. It can be found at: http://dougscripts.com/itunes/scripts/s ... p=embedart

I've done quite a few clean installs although I didn't do it to go to Snow Leopard. A few others things to remember to migrate are:

FontsScriptsColor ProfilesActions for things such as Photoshop or Automator.De-authorizing your machine for iTunes

About the QuickTime MPEG 2 component: unless you got this as part of Final Cut (Pro?), you must have bought this as a download. The component itself is a universal binary, but the installer uses some PowerPC binaries so it won't work anymore under Lion.

WHY I TRIED THIS ON SNOW LEOPARD: I don't have Lion, so that was the only way. I wanted to try this before Lion came out for two reasons: see if manually copying over the iTunes and iPhoto libraries would reduce their sizes a lot. (Not enough to do this for real, I think.) And to provide the Ars readers with the benefit of my experience.

iTunes deauthorization: I thought they removed this option and it happened automatically once you went over 5 authorized systems. Apparently that wasn't true or they went back to the system they used prior to that where you can deauthorize explicitly. But you can always do "deauthorize all" from within your iTunes account.

Why this takes a week: because you need to spend some time with the new machine to discover stuff I forgot to mention that needs to be copied over from the old to the new system. Obviously there are no hard and fast rules about how long this takes but I would be very uncomfortable wiping my old system (even keeping backups) after less than a week.

About the QuickTime MPEG 2 component: unless you got this as part of Final Cut (Pro?), you must have bought this as a download. The component itself is a universal binary, but the installer uses some PowerPC binaries so it won't work anymore under Lion.

I wonder if the installer will get updated when Lion is released.

(An even bigger gripe is why, after all these years and an industry shift towards H.264, that MPEG 2 hasn't been re-licensed so that it's bundled into OS X just for convenience. What a singular nuisance.)

Iljitsch van Beijnum / Iljitsch is a contributing writer at Ars Technica, where he contributes articles about network protocols as well as Apple topics. He is currently finishing his Ph.D work at the telematics department at Universidad Carlos III de Madrid (UC3M) in Spain.